1. Field of the Invention
The present invention relates to a PM (Pulse-Width Modulation) type step motor used for transferring an optical pickup lens or a mobile camera lens of media devices. In detail, the present invention relates to a step motor that is composed of: a stator, a rotor rotating by interacting with the stator, a lead screw combined with the rotor and rotating with the rotation of the rotor, and a bearing supporting the lead screw, which can perform precise transfer because it can perform fine adjustment; and of which the operation state can be precisely sensed by having a position compensator that moves the lead screw to a desired position by finely moving it while contracting and expanding, and a rotation sensing unit which is disposed at a side of the rotor (or a rotary body rotating with the rotor) and senses rotation of the rotor.
2. Description of the Related Art
In general, PM type small-sized step motors used for transferring an optical pickup lens or a camera lens of media devices are used for parts required to control positions such as precise pick-up of an ODD (Optical Disk Drive) or adjustment of the focus of a camera lens.
These step motors can precisely transfer an object, using a lead screw or a gear which has uniform pitches and is disposed at the output side.
Further, with increasing technical development, as various devices have been increasingly manufactured with high precision to be small, there is a need for the ability to more precisely transfer those devices. Thus, for this purpose, there is a need for a step motor having higher driving resolution.
An ‘apparatus for driving lens of optical pick-up’ has been disclosed in Korean Patent No. 10-0632598 and it uses a method of reducing the pitch of a lead screw in sections requiring high precision.
However, it is required to reduce the pitch of a lead screw of a step motor in order to increase resolution for transferring an object, but it is practically difficult to manufacture a lead screw with a pitch of about 0.15 mm or less in mass production due to a mechanical limit in manufacturing.
Accordingly, there is a limit in precise transfer of an object only by reducing the pitch of a lead screw of a step motor.
Further, since there is no part for precisely sensing the operation of a step motor, there is a limit in improving the transfer resolution for an object to be transferred by the step motor.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.